Observation of Meteors for the Years 1932–34 in New Zealand

[Read before the Wellington Philosophical Society, September 25th, 1935; received by the Editor, September 2, 1935; issued separately, June, 1936.]

This report, covering the work performed in the three years 1932–34, is the third published by the Meteor Section of the New Zealand Astronomical Society, Inc., the earlier reports appearing in Transactions of the New Zealand Institute, vol. 60, p. 448 (1927–28) and vol. 63, p. 443 (1929–31), and reprinted as Bulletins 5 and 21 of the New Zealand Astronomical Society, Inc. The present paper is on the same general lines as the preceding reports, to the explanatory portions of which reference should be made.

Practically no meteoric research has been undertaken in the Southern Hemisphere beyond the work done in this country. The section therefore has had an unexplored field in which to work, and the primary objectives necessarily have been to determine the various centres of meteoric radiation south of the celestial equator and to ascertain the rate of meteoric activity and its variation. At the same time no opportunity has been neglected to carry on special studies as far as the limited personnel would permit. While handicapped by little foreknowledge of rates and radiants, the section has benefited from the experience of contemporary bodies in the Northern Hemisphere, and has been able to avoid some of the pitfalls which have retarded northern meteor observers.

The following table summarises the work performed by the various observers during the period covered by the report:—

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The section's work is performed on similar lines to those of the American Meteor Society. The observers record the paths of meteors on special gnomonic maps, at the same time noting details of physical appearance, the whole record requiring less than a minute per meteor for an experienced observer. While every encouragement is given to observers to learn how to reduce their own observations, thereby gaining a lasting interest in meteoric astronomy, all observations are examined by the director, who alone is responsible for the deductions made. The observations are standardised and the reductions uniform. Acknowledgment is due to Dr C. P. Olivier, president of the American Meteor Society, to whom the director is indebted for personal guidance in the past and through whose kindness the recording maps and blanks are supplied to our members.

An important feature of the section's activities lies in the collection of data concerning meteorites and fireballs in this country. This aspect of our work brings the section frequently before the notice of the general public and creates an interest in meteors which it is hoped ultimately will provide additions to the ranks of our regular observers. To facilitate the collection of fireball data from the general public and the prompt notification of any particularly interesting objects, agencies have been established in eleven centres well scattered over the two islands, the majority of agents being persons with experience of meteor-observing. All reports collected are forwarded to the director for examination and publication. In the period covered by this report data of eight fireballs have been collected from 187 observers, while an additional 84 isolated reports of bright meteors have been received.

When the late Dr Malzev, of Tashkent Observatory, found that the newly-discovered comet Peltier-Whipple was likely to provide a southern meteor shower in September, 1932, the information was cabled to the director and a special watch was made in this country by all members of the section. Clouds and moonlight, however, effectively combined to prevent any shower being observed.

The section also co-operated with Byrd's Second Antarctic Expedition, 1934, in the plan for the world-wide observation of meteor rates. Four standard reticles were used in this country, and observations were secured on most of the selected dates. Bad weather, however, frustrated the attempt to secure heights of meteors, for never did more than one station secure clear skies on a selected date.

Elaborate preparations were made to observe the 1932 return of the Leonids, a number of persons not regularly observing being enlisted for the purpose. Moon and clouds once again combined to nullify our efforts, although the director was able to determine a Leonid radiant on November 16. At Hamilton on the night of the expected shower a party of eight observers was on watch. In all £300 worth of cameras and telescopes were employed, but the sky remained clouded throughout.

A list of the most prominent meteor-showers, as revealed by the observations of the section, was published in the second report (Bulletin 21). Below are given notes of further radiants detected in the present period, additional to those previously published:—

Alpha Virginids.—Mean centre of radiation, 206°—10°; observed on April 16. A prominent shower.

Beta Piscid Australids.—335°–35°. July 17 to August 1, five radiants.

Eta Capricornids.—315°–20°. July 23–August 1, four radiants.

Iota Aquarids.—330°–14°. July 26–August 6, six radiants.

Nu Puppids.—100°–44.5° December 5–7 A rich shower.

In a number of instances observed radiants have been found to lie close to the predicted positions of cometary meteor showers. Such cases are tabulated below:—

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In the “Remarks” column D refers to Denning's General Catalogue of Meteor Radiants, the first figures to the group, the final ones to the radiant number; AMS refers to the various lists of the American Meteor Society; BAA to the radiants of the British Astronomical Association; numbers without initial letters, or in some cases with NZ prefixed, refer to the radiants published by the Meteor Section of the New Zealand Astronomical Society, Inc. TC to Circulars of the Tashkent Observatory.

Explanation of Tables

Table I.—Details of Observations. This table gives details of the watches performed by the various observers, and is similar in form to those in the previous reports. The rate actually observed per hour (column 6) is corrected by a factor (column 7) which attempts to make allowance for hindrances to observation, such as clouds or moonlight the corrected rate being given in column 8. The estimation of rates has not been attempted for very short watches or in cases where the hindrance to observation was too great for any certainty to be attached to the factor.

Table II.—List of Radiants. This follows the form in the preceding report, being arranged in order of date. At least four meteors observed on one night and intersecting in a circle 2° in diameter, or at least five on adjacent nights, or one stationary meteor being required to form these radiants.

The numerous statistical tables published in previous reports will not be included in future. The collection of the statistics is being continued, however, and eventually will be made the subject of a special paper.

Conclusion.

The need for additional meteor observers in the Southern Hemisphere, and especially in this country, remains acute. Although the section has contributed considerable data to our knowledge, or lack of knowledge, of the southern meteor showers, the need for a larger annual output is revealed by the work remaining to be done. In the past ten years, for example, there were 150 dates in the year on which no observations were secured, while on a further 109 days observations have been secured only once in the period. On only 106 days of the year have observations been secured more than once. The months from March to August have been fairly satisfactorily covered by observers, but for the months September to February inclusive, the most comfortable observing period of the year, observations are very few in number, although there are indications that some fairly high rates of meteoric activity can be secured in the period.